GB-A-2121762 describes sealed beverage packages containing a product for preparing a beverage in admixture with water, the package comprising a sachet of flexible film material and an integral nozzle for water injection into the package. The beverage escapes from the package through an outlet made by the user cutting open the bottom of the package, or the package may comprise means for enabling a user to open the base of the sachet easily, for example peelable tabs, edge nicks, tear strings or tear strips. However, in each case the intervention of a user is needed to open the bottom of the sachet.
EP-A-0179641 describes a related beverage brewing system, in which the package is a sachet of flexible film material with an integral nozzle for water injection. The bottom edge of the beverage sachet is sealed by bonding together two sheets of flexible film material with a pressure-sensitive adhesive. When the interior of the sachet is pressurised by injection of water to brew beverage, the resulting pressure in the sachet separates the pressure-sensitive adhesive, thereby allowing the beverage to flow out of the bottom of the sachet. This beverage brewing system has enjoyed great commercial success. However, the need to apply a pressure sensitive adhesive adds to the complexity of manufacturing these sachets. Furthermore, the sachets described in this reference are not biodegradable or compostable.
Polylactic acid and lactic acid copolymers are thermoplastic and biodegradable and compostable. When the polymers are placed in soil or sea water, the polymers start to decompose. In a compost, these materials biodegrade rapidly. The degradation products of these polymers are lactic acid, carbon dioxide and water, all of which are nontoxic.
Polymers of lactic acid are usually prepared from a cyclic dimer of lactic acid which is called lactide. In a typical copolymerization of lactic acid, lactide and glycolide, (a dimer of glycolic acid) are mixed, and ring-opening polymerization is carried out. In the alternative, the polymers may be prepared directly by condensation of lactic acid or a mixture of lactic acid and glycolic acid, but in these direct condensations a high molecular weight polymer cannot be obtained even if the reaction is carried out for a long time. On the other hand, the ring-opening polymerization of lactide or of a mixture of lactide and glycolide can provide a high molecular weight straight-chain polyester. Suitable polymerisation processes are described in EP-A-0624615 and WO-A-02100921.
Lactic acid polymers and copolymers are thermoplastic, but heat sealing of films of such polymers is difficult because of heat distortion and shrinkage of the films, and because the films tend to stick to the sealing jaws of the heat sealing apparatus.
EP-A-0514137 describes degradable laminates comprising a surface layer of a polylactide polymer or copolymer, wherein the surface layer is laminated to a layer of regenerated cellulose, film, paper, leather or cloth.
US-B-6183814 describes paper substrates coated with a layer of compostable polylactide. The resulting coated papers are suitable for making e.g. compostable paper cups. The paper may be sequentially coated with two layers of different polylactides onto the paper substrate.
U.S. Pat. No. 6,153,276 describes heat-sealable laminates of PLA. The laminates comprise a substrate layer of crystalline PLA having a high melting point, and a sealing layer of amorphous PLA having a lower melting point. There is no disclosure of applying such laminates to a printable substrate.